1. Field of the Invention
The present invention relates to a musical tone waveform signal forming apparatus utilized in electronic musical instruments, reverberation apparatuses, toys, and the like and, more particularly, to a musical tone waveform signal forming apparatus for receiving a musical tone control signal for steadily or time-serially controlling musical tone parameters such as a pitch, a tone color, a tone volume, and the like of a musical tone, and forming a musical tone waveform signal according to the input musical tone control signal.
2. Description of the Prior Art
As disclosed in, e.g., Japanese Patent Laid-Open No. Sho 63-40199, a conventional apparatus of this type comprises a waveform signal transmission section constituted by a plurality of signal transmission units which are connected in cascade one by one and each of which comprises a first signal line serving as a forward path of a waveform signal, a second signal line serving as a backward path of the waveform signal, and a node portion for attenuating an output from the first signal line, transmitting the attenuated output to the next stage, and feeding back the output from the first signal line to an input side of the second signal line, at least one of the first and second signal lines serving as a signal delay line., a musical tone control signal input section for receiving a waveform signal from the waveform signal transmission section and a musical tone control signal for controlling musical tone parameters of a musical tone to be generated, changing the waveform signal in accordance with the musical tone control signal, and outputting the changed waveform signal to the waveform signal transmission section., and a pitch control section for changing attenuation coefficients and feedback coefficients of the respective node portions in accordance with a pitch control signal for controlling a pitch of the musical tone control signal. The musical tone control signal input section corresponds to a mouthpiece of a wind instrument, the waveform signal transmission section corresponds to a resonance tube of a wind instrument, and the node portions in the waveform transmission section correspond to tone holes of the wind instrument, so that a musical tone control signal according to performance data is inputted to the musical tone signal input section and the pitch control section, and a waveform signal is generated according to the input musical tone control signal, thereby generating a musical tone imitating a musical tone of the wind instrument, or the like.
More specifically, in the conventional apparatus, pitch control is performed by simulating tone holes of the wind instrument, and the delay times of delay lines corresponding to a flared tubular shape of the wind instrument are set to be constant. Therefore, it is difficult to change a pitch at an interval smaller than that determined by tone hole intervals.